KR20100069950A - Solar cell's electrode, manufacturing method thereof, and solar cell - Google Patents

Abstract

PURPOSE: An electrode for a solar cell, a manufacturing method thereof, and the solar cell are provided to obtain a high aspect ratio of the electrode and improve contact between the substrate and the conductive electrode material by printing and plasticizing the electrode using a binder with high tg to improve the aspect ratio after using the binder with low Tg to improve the contact. CONSTITUTION: A composition for a solar cell electrode(20) is printed on a substrate(10). A binder polymer for the composition for the solar cell is the binder polymer with low Tg. An aspect ratio is improved by the reinforcement and print using the composition for the solar cell electrode with the binder with high Tg.

Description

Solar cell electrode, manufacturing method and solar cell {Solar Cell's Electrode, Manufacturing Method Thereof, And Solar Cell}

The present invention relates to a solar cell electrode, a manufacturing method thereof and a solar cell.

A solar cell is a semiconductor device that converts solar energy into electrical energy and has a p-n junction. The basic structure is the same as that of a diode. When light is incident on the solar cell, it is absorbed and interacts with the material constituting the semiconductor of the solar cell. As a result, the formed minority carriers, electrons and holes, are connected to each other before recombination. The electromotive force is obtained by drift to the electrode.

Generally, crystalline silicon solar cells can be classified into single crystal and polycrystalline forms. Single crystal is a high-quality material with high purity and low crystal defect density, but of course, high efficiency is relatively high. Expensive and polycrystalline materials are commonly used because they are less efficient than single crystals but relatively inexpensive.

First, a method of manufacturing a polycrystalline silicon solar cell is a defect of a surface of a polycrystalline silicon substrate which is intended to use a p-type substrate having a constant size (5 or 6 "for a commercially available substrate size) and a thickness (150-250 µm) by an appropriate etching method. After removing the P-substrate containing POCl3 or P in a gaseous or liquid phase by a thermal diffusion method (doping the surface of the p-type substrate to a constant thickness (0.1 ~ 0.3 ㎛) to make an n-type semiconductor. Then, wet etching process using acid or base is included to remove by-products such as phosphorus-containing glass generated in this process, and plasma is removed to remove doped P in the remaining parts except for the part irradiated with light. Used dry etching process is included. Then, in order to increase the efficiency of the solar cell, crystalline or amorphous silicon nitride, silicon oxide, titanium oxide, or a combination thereof is deposited by an appropriate thickness (about 70 to 90Å for silicon nitride) by physical vacuum deposition. Thereafter, the P-type semiconductor layer electrode and the N-type semiconductor layer electrode are printed and dried at a constant line width and height by a printing method (usually screen printing). In particular, the solar irradiation surface electrode generally contains silver and the line width is set to about 100 μm at a height of 100 μm. The opposite electrode generally screen-prints and dries an electrode made of a combination of aluminum, aluminum and silver to a constant thickness, taking into account bowing of the substrate. Thereafter, it is fired for several seconds to several hundred seconds at a relatively high temperature of 700 to 900 ° C so that the conductive metals of the front and rear electrodes come into contact with each semiconductor layer to have a function as an electrode.

In the general solar cell manufacturing process as described above, in particular, a line width of about 80 to 120 μm is printed by using screen printing during front electrode (bus electrode and / or finger electrode) printing, and the quality of the line shape is not good. There are various problems such as poor workability due to platelet blockage during repeated printing, difficulty in multilayer printing, and low aspect ratio during firing.

In the present invention, in order to solve the above problems, the electrode is printed in a multi-layer, by using a conductive paste in which the glass transition temperature and the solvent boiling point of the binder is different for each layer by printing by printing methods such as gravure offset, the aspect ratio is high and the substrate It is an object of the present invention to provide a solar cell electrode manufacturing method having good contact with a conductive electrode material and a solar cell having high cell efficiency.

As a means for solving the above problems,

The present invention provides a method for producing a solar cell electrode through a printing method using a composition for a solar cell electrode comprising a binder polymer, a diluent solvent, a metal electrode material, and a glass powder, the contact between the substrate and the electrode on the substrate Printing the composition of the binder polymer is a low Tg binder polymer for properties; and reinforcing printing the composition of the binder is a high Tg binder polymer to improve the aspect ratio; Provide a method.

Tg of the low Tg binder polymer is in the range of -40 ~ 10 ℃, Tg of the high Tg binder polymer is preferably in the range of 50 ~ 120 ℃.

If necessary, the method may further include printing the composition with the heavy Tg binder polymer between the step of printing with the composition to which the low Tg binder polymer is applied and the step of reinforcing printing with the composition to which the high Tg binder polymer is applied. The Tg of the Tg binder polymer has a value between the Tg of the low Tg binder polymer and the Tg of the high Tg binder polymer.

In addition, the present invention makes it possible to produce an excellent electrode even with a gravure offset printing method.

In addition, the electrode aspect ratio (height / width) after the step of reinforcing printing with a composition to which the high Tg binder polymer is applied, provides a method for producing an electrode, characterized in that 0.3 ~ 1.0. The electrode manufactured by the above manufacturing method has a width of 30 to 100 μm and a height of 30 to 100 μm.

The present invention also provides a substrate for a solar cell having a bus electrode and a finger electrode on the substrate, wherein at least one of the bus electrode and the finger electrode comprises a lower printed layer printed with a conductive paste composition using a low Tg polymer binder. Provided is a substrate for a solar cell, wherein an electrode including an upper printed layer printed with a conductive paste composition using a high Tg polymer binder is fired and formed.

In addition, at least one of the bus electrode and the finger electrode has an electrode width of 30 to 100 µm, a height of 30 to 100 µm, and an electrode aspect ratio (height / width) of 0.3 to 1.0.

The present invention also provides a solar cell including a bus electrode and a finger electrode on an upper substrate, and a back electrode on a lower substrate, wherein at least one of the bus electrode and the finger electrode uses the above-described solar cell electrode manufacturing method. To provide a solar cell or a solar cell provided with the solar cell substrate, the cell efficiency is 17% or more.

In the solar cell electrode manufacturing method and solar cell of the present invention, a low Tg binder (hereinafter referred to as Tg) is first used for good contact between a substrate such as a silicon wafer and a conductive electrode material. Since the electrode is printed and fired using a high binder (hereinafter Tg), the aspect ratio of the electrode is high, the contact between the substrate and the conductive electrode material is good, and the cell efficiency is excellent.

Hereinafter, the present invention will be described in more detail with reference to the drawings and embodiments. The following descriptions are for specific examples of the present invention, but are not intended to limit the scope of the rights set forth in the claims, even if there is an assertive or limited expression.

Solar cell electrode manufacturing method according to an embodiment of the present invention, a method for producing a solar cell electrode through a printing method using a composition for a solar cell electrode comprising a binder polymer, a diluent solvent, a metal electrode material, and glass powder. In the upper part of the substrate, for printing the composition of the binder polymer is a low Tg binder polymer for the contact characteristics of the substrate and the electrode, and the reinforcement printing of the composition of the binder is a high Tg binder polymer for improving the aspect ratio Characterized in that it comprises a.

1 is a schematic cross-sectional view of an electrode manufactured by a solar cell electrode manufacturing method according to an embodiment of the present invention, the lower printed layer 20 printed with a conductive paste composition using a low Tg polymer binder on the substrate 10 And an electrode comprising an upper print layer 30 printed with a conductive paste composition using a high Tg polymer binder.

As the composition for solar cell electrodes, any conductive paste composition that can be applied to solar cell electrodes and capable of forming electrodes by a printing method is included. As a preferable example, the electrically conductive paste composition containing a binder, a diluent, a conductive metal material, a glass frit, and an inorganic thixotropic agent is mentioned. According to a preferred embodiment, the composition according to the invention comprises 1 to 20% by weight binder, 5 to 25% by weight diluent, 60 to 90% by weight conductive metal material, 1 to 10% by weight glass frit and 0.1 to 5 It may include weight percent additives.

In the present invention, it was found that the selection of the binder included in the composition has a great influence on the characteristics of the electrode and the solar cell efficiency.

In general, during firing after electrode printing, the flowability increases due to the low viscosity paste rheological properties and the paste self loading in the high temperature process, and thus, it is difficult to maintain an electrode having a predetermined height or more during the firing process. In the present invention, in particular, the glass transition temperature of the binder is controlled among the materials of the conductive paste, and when the high Tg binder polymer having a Tg of 50 ° C. or more and preferably 100 ° C. or more is applied, there is almost no change in aspect ratio before and after firing, unlike the conventional conductive paste. . However, when printing with a paste to which the same Tg binder was applied, the contact property between the substrate and the electrode, such as a Si wafer, was disadvantageous, resulting in a decrease in efficiency. The present invention solves the problem of changing the aspect ratio after firing by varying the binder Tg of the electrode material of each layer when forming the electrode by the gravure offset method, and at the same time solves the disadvantages of the contact property between the substrate and the electrode due to the high Tg of the binder. This increases the efficiency of the solar irradiation surface is wider. That is, by controlling the binder glass transition temperature of the layered material, unlike the conventional conductive paste, there is almost no change in the aspect ratio before and after firing, and as a result, the efficiency of the solar irradiation surface is widened.

Specifically, in the present invention, when the electrode is printed first, the electrode is first printed using the low Tg binder polymer to improve the contact between the electrode and the substrate, and then the aspect ratio of the electrode is increased by reinforcement printing using the high Tg binder polymer. This can be significantly increased. Tg of the low Tg binder polymer is preferably in the range of -40 ~ 10 ℃, Tg of the high Tg binder polymer is preferably in the range of 50 ~ 120 ℃. If necessary, the method may further include the step of printing with a composition applied with the heavy Tg binder polymer between the step of printing with a composition to which the low Tg binder polymer is applied and the step of reinforcing printing with a composition to which the high Tg binder polymer is applied. The Tg of the heavy Tg binder polymer has a value between the Tg of the selected low Tg binder polymer and the Tg of the selected high Tg binder polymer.

Although the binder used in the conductive paste composition according to the embodiment of the present invention is not limited, cellulose acetate, cellulose acetate butylate, and cellulose ether compound may be ethyl cellulose, methyl cellulose, hydroxy flofil cellulose, or hydroxy. Ethyl cellulose, hydroxy propyl methyl cellulose, hydroxy ethyl methyl cellulose, polyacrylamide, poly methacrylate, poly methyl methacrylate, polyvinyl methacrylate, polyvinyl butyral, polyvinyl At least one or more of acetate and polyvinyl alcohol may be selected and used. It is preferable that the molecular weight of the said acryl-type compound is 5,000-50,000.

The low Tg binder used in the conductive paste composition according to the embodiment of the present invention is ethyl acrylate (EA), hydroxy ethyl acrylate (HEA), hydroxy propyl acrylate (HPA), 2-ethyl nuclear chamber acrylate (2 -EHA), butyl acrylate (BA), stearyl methacrylate (SMA), vinyl butyl ether (VBE), vinyl ethyl ether (VEE), vinyl isobutyl ether (VIE), vinyl methyl ether (VME), heavy A binder synthesized of at least one or more kinds may be used, and the high Tg binder used in the conductive paste composition according to the embodiment of the present invention may be acrylic acid (AA), methyl acrylic exit (MAA), methyl methacrylate ( MMA), ethyl methyl acrylate (EMA), isobutyl meth acrylate (i-BMA), 2-hydroxy ethyl methyl acrylate (2-HEMA), styrene monomer (SM), glycidyl methacrylate ( GMA), arc In addition to the acrylic binder synthesized with amide (AAM), acrylonitrile (AN), methacrylo nitrile (MAN), etc., ethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose cellulose) and cellulose derivatives of hydroxyethylhydroxypropyl cellulose can be used including.

Diluents used in the composition according to one embodiment of the invention alpha-terpineol, texanol, dioctyl phthalate, dibutyl phthalate, cyclohexane, hexane, toluene, benzyl alcohol, dioxane, diethylene glycol, ethylene glycol It is preferable to use at least one selected from compounds consisting of mono butyl ether, ethylene glycol mono butyl ether acetate, diethylene glycol mono butyl ether, diethylene glycol mono butyl ether acetate, and the like.

As the conductive metal material used in the conductive paste according to the embodiment of the present invention, silver powder, copper powder, nickel powder, aluminum powder, and the like may be used, among which silver powder is most preferred. For convenience, the conductive metal material will be described using silver powder as an example.

The silver powder has an average particle diameter of 0.5 to 5 µm, and the shape may be at least one of spherical, acicular, plate and amorphous. The average particle diameter of the silver powder is preferably 0.5 μm to 5 μm in consideration of ease of pasting and density at firing. In addition, the content of the silver powder is preferably 60 to 90% by weight based on the total weight of the conductive paste composition in consideration of the electrode thickness and the wire resistance of the electrode formed during printing.

Glass frit used in the composition according to an embodiment of the present invention has an average particle diameter of 0.5 ~ 5㎛, its components, PbO 43 ~ 91 wt%, SiO2 21 wt% or less, B2O3 + Bi2O3 25 wt% or less, Al2O3 It is preferable that at least one or more of glass powders having 7 wt% or less, ZnO 20 wt% or less, Na 2 O + K 2 O + Li 2 O 15 wt% or less, and BaO + CaO + MgO + SrO 15 wt% or less have a glass softening temperature of 320 to 520 ° C. And the coefficient of thermal expansion are preferably 62 to 110 × 10 −7 / ° C. The content of the glass frit is preferably 1 to 10% by weight based on the total weight of the conductive paste composition. If the content is less than 1% by weight, incomplete firing may occur to increase the electrical resistivity. There are too many components, and there exists a possibility that an electrical resistivity may also become high.

The composition according to the present invention may further include additives commonly known as necessary, for example, a dispersant, a defoamer, and a leveling agent.

The conductive paste composition according to the present invention is useful for producing surface electrodes of photovoltaic cells.

In order to manufacture an electrode using the conductive paste composition according to the present invention, first, a step of patterning the conductive paste composition having different Tg properties of the binder according to the present invention by direct multilayer printing on a substrate, and drying the printed electrode paste And forming the electrode by firing the printed electrode paste.

The conductive paste composition according to the present invention can be printed on a substrate using a variety of printing methods such as screen printing, gravure offset method, rotary screen printing method or lift off method, preferably a gravure offset method easy to fine pattern This is good. The electrode thus formed preferably has a thickness of 10 to 40 µm.

The electrode paste patterned with the conductive paste composition according to the present invention may be dried for several minutes at a temperature of 150 to 250 ℃ and calcined for several seconds at a temperature of 700 to 900 ℃.

When the conductive paste composition having different Tg properties of the binder is printed by multi-layer printing directly on the substrate, a preferred example will be described below.

The electrode paste for solar cells according to the present invention is a front electrode paste for solar cells which is calcined at 700 ~ 900 ℃, the total paste of the electrode is 49 ~ 85 wt% metal powder, 1 ~ 10 wt% glass powder, organic material It has a weight fraction of 9 to 50 wt%, and when the silver metal is used as the metal powder, the average particle diameter is 0.5 to 15 µm, and its shape is spherical, acicular, and plate-shaped. ) And at least one of amorphous phases, the glass powder has an average particle diameter of 0.5 to 5 µm, and the component thereof is SiO2. At least 1 in glass powders of 21 wt% or less, B2O3 + Bi2O3 25 wt% or less, Al2 O3 7wt% or less, ZnO 20 wt% or less, Na2O + K2O + Li2O 15 wt% or less, BaO + CaO + MgO + SrO 15 wt% or less It is composed of more than one species, the glass softening temperature is 320 ~ 520 ℃, the coefficient of thermal expansion is 62 ~ 110 × 10-7 / ℃, the organic material is a polymer binder 2 ~ 5 wt%, diluent solvent 3 ~ 20 wt%, Additive is 2-5 wt%.

First, the electrode paste for solar cells according to the present embodiment is a 49 to 85 wt% silver metal powder as the main component of the electrical conductivity of the whole paste, glass powder 1 to 10 to promote sintering and improve the interfacial adhesion between the crystalline silicon wafer substrate and the electrode wt%, 9-50 wt% organic matter supporting these powders, and 2-5 wt /% additives including other rheology modifiers and dispersants, leveling agents and the like.

When the silver metal is used as the metal powder, the average particle diameter is 0.5 to 15 µm, and the shape thereof is at least one of spherical, acicular, plate-like, and amorphous. It consists of more than one species. If the average particle diameter of the silver powder is 0.5 μm or less, it is generally difficult to make a paste. If the average particle size of the silver powder is 15 μm or more, it is difficult to densify sufficiently during firing and pores are easily generated, resulting in high electrical resistivity. If the content of the silver powder is 49 wt% or less, the resistance of the electrode for solar cells is high, and if the content of the silver powder is 85 wt% or more, the viscosity of the electrode is too high, and electrode printing is difficult in a commercially available printing method.

The glass powder comprises a weight fraction of 1 to 10 wt% of the total paste, 21 wt% or less of SiO2, 26 wt% or less of B2O3, 25 wt% or less of Bi2O3, 7 wt% or less of Al2O3, 20 wt% or less of ZnO, Na2O + K2O + Li2O 15 wt% or less, BaO + CaO + MgO + SrO It consists of at least one or more of the glass powders.The glass softening temperature is 320 ~ 520 ℃ and the thermal expansion coefficient is 62 ~ 110 × 10- In the 7 / ° C range. If the SiO2 is 21 wt% or more, the softening temperature is high, and thus the sintering degree is lowered. If the B2O3 + Bi2O3 is 25 wt% or more, the softening point is high and fluidity is inferior. In addition, when Al2O3 is 7 wt% or more, the softening temperature is high, and when ZnO is 35 wt% or more, the viscosity change is slowed at high temperature. If the + MgO + SrO is more than 15 wt%, the softening temperature is high, resulting in poor fluidity. In addition, when the content of the glass powder with respect to the entire paste in the paste is 1 wt% or less, incomplete firing is formed, and the electrical resistivity is high. Too high. The glass softening temperature of the glass powder is 320 ~ 520 ℃, thermal expansion coefficient is in the range of 62 ~ 110 × 10-7 / ℃. When the glass softening temperature of the glass powder is 520 ° C or higher, the fluidity is lowered and the plasticity is lowered. When the glass softening temperature is 320 ° C or lower, the fluidity is too high and the plasticity is lowered. When the thermal expansion coefficient of the glass powder is 62 × 10 −7 / ° C. or less, breakage of the electrode occurs during firing of the formed electrode. When the glass powder has a thermal expansion coefficient of 110 × 10 −7 / ° C. or more, the straightness of the formed electrode decreases.

The organic material is largely composed of a binder of 2 to 15 wt%, a diluent of 4 to 35 wt%, and an additive of 2 to 5 wt%. First, the binder component is a cellulose ester compound, a cellulose acetate, a cellulose acetate butylate, and a cellulose ether compound are ethyl cellulose, methyl cellulose, hydroxy flophyll cellulose, hydroxy ethyl cellulose, hydroxy propyl methyl cellulose, hydroxy ethyl methyl Cellulose and acryl-based compounds include polyacrylamide, polymethacrylate, polymethylmethacrylate, and polyethylmethacrylate. The vinyl-based compound is composed of at least one of polyvinyl butyral, polyvinyl acetate, and polyvinyl alcohol. . When the binder amount is 15 wt% or more, the electrode width in one printing (average value of the maximum width values of the fired body after printing and the minimum widths of the fired body after printing, referred to as the electrode width below). Since the ratio of the electrode height to the substrate is printed as low as 4% or less, the number of prints for increasing the line resistance of a predetermined value or less increases, and when the binder component is 2 wt% or less, the binder forms the shape of the electrode until firing. There is a problem that can not play the original role to maintain.

The binder component acts as a master to adjust the viscosity of the entire paste, and the viscosity of the entire paste should be between 5,000 and 300,000 cps. Viscosity has a significant effect on the firing spread rate of the electrode (increase ratio to the average value of the maximum width values of the fired electrode after printing the electrode on the glass substrate with respect to the screen mask electrode pattern width value). Is 5,000 cps or less, the spread ratio is increased to 105% or more, and if the viscosity of the whole paste is 100,000 cps or more, printability is poor and breakage of the electrode frequently occurs.

The dilution solvent component is characterized by consisting of at least one or more of compounds consisting of terpineol, cyclohexane, hexane, toluene, benzyl alcohol, dioxane, diethylene glycol and the like. If the dilution solvent component is 35 wt% or more, the paste viscosity is very low, it is difficult to print with a commercialized printing equipment, even if printing, shrinkage during curing is too severe to use. Moreover, when it is 4 weight% or less, the screen mask omission property of the said paste will worsen, and the unevenness | corrugation of a printed electrode will become large, and the problem that the electrical wire resistance of an electrode becomes high compared with the printed area arises.

Forming an electrode pattern with a paste having the composition as described above, in particular, the most important physical properties in the pattern formation is characterized in that the viscosity is 5,000 ~ 300,000 cps (Measurement conditions HAAKE TT35 Plate, 25 ℃, 50rpm) Viscosity 5,000 If it is less than cps, it becomes larger than the existing design line width, If the viscosity of the whole paste is 100,000 cps or more, print workability will fall and breakage of an electrode will occur frequently. In addition, the thixotropic index (viscosity at TI = 5 rpm / viscosity at 50 rpm) greatly affects the shape retention of the pattern after printing and has a value of 1.5 to 5.5.

 Photovoltaic cells produced using the compositions of the present invention may have additional elements to enhance their function. For example, a welding layer may be provided on the surface of the surface electrode to improve the reliability of battery performance.

A solar cell substrate having a bus electrode and a finger electrode on a substrate, wherein at least one of the bus electrode and the finger electrode is printed by a conductive paste composition using a low Tg polymer binder by the manufacturing method described above. And the electrode comprising a top printed layer printed with a conductive paste composition using a high Tg polymer binder is formed by firing, the electrode width is 30 ~ 100㎛ prepared in this way, the height can be manufactured in the range of 30 ~ 100㎛ And the electrode aspect ratio (height / width) provides 0.3-1.0.

Since the surface electrode formed from the conductive paste according to the present invention can realize an aspect ratio (height / width) of 0.3 or more, if the surface electrode is applied to a solar cell, the light receiving area of the solar cell can be increased to 93% or more. . In addition, the conductive paste according to the present invention makes it possible to efficiently use the electromotive force generated by light reception as a current because the line resistance decreases when firing. As a result, more than 17% of solar cell efficiency can be realized.

  [Production Example 1]

100 g of butylcatitol acetate (BCA) was added to a 2 L flask, and the mixture was maintained at 100 ° C. while stirring. Here, 35.5 g of methyl methacrylate (MMA), 8.5 g of styrene monomer (SM), 30 g of hydroxyethyl methacrylate (HEMA), 11 g of methylacrylic acid (MAA) and 5 g of benzyl peroxide were dissolved. Dropwise over time. After standing for 1 hour, 0.15 g of benzyl peroxide dissolved in 20 g of BCA was added to confirm the exothermic condition. If the exotherm did not occur, the reaction was considered to be completed. Methaacrylate-methacrylic acid) resin binder 1 was prepared.

15 g of the prepared binder 1, 1 g of a dispersant (BYK110, BYK chemi), and 5 g of frit (average particle diameter: 1 µm) were added and dispersed using a three-bone mill, and 38 g of silver powder (spherical, average particle diameter: 1 µm), silver powder (Flake) 40 g of an average particle diameter of 3 µm) were mixed and further dispersed using a sambon mill. Thereafter, degassing under reduced pressure to prepare a conductive paste.

[Production Example 2]

100 g of butylcatitol acetate (BCA) was added to a 2 L flask, and the mixture was maintained at 100 ° C. while stirring. Here, 21.5 g of methyl methacrylate (MMA), 30 g of beryl acrylic monomer (BAM), 8.5 g of styrene monomer (SM), 20 g of hydroxy ethyl methacrylate (HEMA), 15 g of methyl acrylic acid (MAA), and benzylper A solution of 5 g of oxide was added dropwise over 3 hours. After standing for 1 hour, 0.15 g of benzyl peroxide dissolved in 20 g of BCA was added to confirm the exothermic condition. If the exotherm was not obtained, the reaction was considered to be completed. Methacrylate-methacrylic acid) resin binder 2 was prepared.

15 g of the prepared binder 2, 1 g of a dispersant (BYK110, BYK chemi), and 5 g of frit (average particle diameter: 1 μm) were added and dispersed using a three-bone mill, and 38 g of silver powder (spherical, average particle diameter: 1 μm) and silver powder (Flake) 40 g of an average particle diameter of 3 µm) were mixed and further dispersed using a sambon mill. Thereafter, degassing under reduced pressure to prepare a conductive paste.

[Manufacture example 3]

100 g of butylcatitol acetate (BCA) was added to a 2 L flask, and the mixture was maintained at 100 ° C. while stirring. Here, 5 g of methyl methacrylate (MMA), 57 g of beryl acrylic monomer (BAM), 6 g of styrene monomer (SM), 15 g of hydroxy ethyl methacrylate (HEMA), 7 g of acrylic acid (AA), and 10 g of benzyl peroxide were added thereto. The dissolved solution was added dropwise over 3 hours. After standing for 1 hour, 0.15 g of benzyl peroxide dissolved in 20 g of BCA was added to confirm the exothermic condition. If the exotherm did not occur, the reaction was considered to be completed. Methyl methacrylate-methacrylic acid) resin binder 3 was prepared.

15 g of the binder 3 prepared above, 1 g of a dispersant (BYK110, BYK chemi), 5 g of frit (average particle diameter: 1 μm), and dispersed using a three-bone mill, 38 g of silver powder (spherical, average particle diameter: 1 μm), silver powder (Flake) 40 g of an average particle diameter of 3 µm) were mixed and further dispersed using a sambon mill. Thereafter, degassing under reduced pressure to prepare a conductive paste.

The compositions shown in each of the preparation examples are summarized in Table 1 below.

TABLE 1

Preparation Example 1 Preparation Example 2 Preparation Example 3 bookbinder 15 (Tg 87 ℃) 15 (Tg 26 ℃) 15 (Tg -19 ℃) diluent 2.0 2.0 2.0 Slip 1.0 1.0 1.0 Dispersant 1.0 1.0 1.0 Silver powder 78 78 78 Glass powder 3 3 3 Sum 100 100 100

In addition, the theorem of the multilayer printing method of each of the above examples is summarized in Table 2 below, and the aspect ratio, line width, height, and cell efficiency of the electrodes are measured and shown in Table 3 and FIGS. 2 and 3.

TABLE 2

Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 Stacking count 3 3 3 3 1 layer electrode material Manufacture 3 Manufacture 1 Manufacture 2 Manufacture 3 2-layer electrode material Manufacture 1 Manufacture 1 Manufacture 2 Manufacture 3 3-layer electrode material Manufacture 1 Manufacture 1 Manufacture 2 Manufacture 3

[Table 3]

Aspect ratio (height / width) Height [㎛] Line width [㎛] Cell efficiency (%) Example 1 0.428 19.3 45.1 18.9% Comparative Example 1 0.496 21.2 42.7 8.9% Comparative Example 2 0.276 13.5 49 15.8% Comparative Example 3 0.096 6.06 62.8 13.6%

In Table 3 and FIGS. 2 and 3, when the binder glass transition temperature is low, the cross section after firing collapses and the aspect ratio is significantly worse (Comparative Example 3). The higher the binder glass transition temperature, the better the aspect ratio. It can be seen that the cell efficiency is significantly decreased (Comparative Example 1). On the contrary, in the case of Example 1, which was first printed with a low Tg binder polymer and then reinforced with a high Tg binder polymer, the cross-sectional collapse of the print was reduced even after firing, so that the aspect ratio was excellent and the cell efficiency was also excellent. In addition, the present inventors have realized a sufficient thickness of 10 ㎛ or more and a line width of 50 ㎛ or less through a characteristic multilayer printing method.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram of electrode paste lamination which applied the binder from which Tg applied by this invention differs.

2 is an electrode cross-sectional photograph obtained through heat treatment at 800 ° C. for 20 seconds after laminating electrode compositions of Example 1 and Comparative Examples 1 to 3. FIG.

3 is a photograph for evaluating contact characteristics between Si wafers and electrodes of Example 1 and Comparative Example 1. FIG.

** Description of the main symbols in the drawings **

10: substrate

20: low Tg binder polymer electrode paste lower printing layer

30: High Tg Binder Polymer Electrode Paste Top Printing Layer

Claims (14)

In the method for producing a solar cell electrode through a printing method using a composition for a solar cell electrode comprising a binder polymer, a diluent solvent, a metal electrode material, and glass powder, Printing on the substrate with a composition for solar cell electrodes wherein the binder polymer is a low Tg binder polymer for contact characteristics between the substrate and the electrode; and the binder is a high Tg binder polymer for improving the aspect ratio. Reinforcing printing step; solar cell electrode manufacturing method comprising a. The method of claim 1, wherein the Tg of the low Tg binder polymer is in the range of -40 ~ 10 ℃. The method of claim 1, wherein the Tg of the high Tg binder polymer is in the range of 50 to 120 ℃. The method of claim 1, wherein the low Tg binder polymer is ethyl acrylate (EA), hydroxy ethyl acrylate (HEA), hydroxy propyl acrylate (HPA), 2-ethyl nuclear chamber acrylate (2-EHA), At least one of butyl acrylate (BA), stearyl methacrylate (SMA), vinyl butyl ether (VBE), vinyl ethyl ether (VEE), vinyl isobutyl ether (VIE), vinyl methyl ether (VME) Method for producing a solar cell electrode, characterized in that selected. The method of claim 1, wherein the high Tg binder polymer is acrylic acid (AA), methyl acrylic exit (MAA), methyl meth acrylate (MMA), ethyl methyl acrylate (EMA), isobutyl meth acrylate (i-BMA). ), 2-hydroxy ethyl methyl acrylate (2-HEMA), styrene monomer (SM), glycidyl methacrylate (GMA), acrylamide (AAM), acrylonitrile (AN), methacrylo Cellulose of ethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose and hydroxyethyl hydroxypropyl cellulose Method for producing an electrode for a solar cell, characterized in that at least one selected from derivatives. The method of claim 1, further comprising the step of printing with a composition applying the heavy Tg binder polymer between the step of printing with a composition to which the low Tg binder polymer is applied and the step of reinforcing printing with a composition to which the high Tg binder polymer is applied. Solar cell electrode manufacturing method. The method of claim 6, wherein the Tg of the Tg binder polymer is between the Tg of the low Tg binder polymer and the Tg of the high Tg binder polymer. The method for manufacturing an electrode for solar cells according to any one of claims 1 to 7, wherein the printing method is a gravure offset printing method. 8. The aspect of any one of claims 1 to 7, wherein the aspect ratio (height / width) of the electrode after calcining after reinforcing printing with the composition to which the high Tg binder polymer is applied is 0.3 to 1.0. Battery electrode manufacturing method. A solar cell electrode manufactured by the manufacturing method of any one of claims 1 to 7, wherein the electrode width is 30 ~ 100㎛, the height is 30 ~ 100㎛, the electrode aspect ratio (height / width) is 0.3 ~ 1.0 Solar cell electrode, characterized in that. A solar cell substrate having a bus electrode and a finger electrode on an upper substrate, wherein at least one of the bus electrode and the finger electrode includes a lower printed layer and a high Tg polymer binder printed with a conductive paste composition using a low Tg polymer binder. An electrode comprising a top printed layer printed with a conductive paste composition is formed by firing the substrate for a solar cell. The method of claim 11, wherein at least one of the bus electrode and the finger electrode has an electrode width of 30 to 100 μm, a height of 30 to 100 μm, and an electrode aspect ratio (height / width) of 0.3 to 1.0. Solar cell substrate. In the solar cell having a bus electrode and a finger electrode on the upper substrate, and a back electrode on the lower substrate, At least one or more of the bus electrode and the finger electrode is manufactured using the solar cell electrode manufacturing method of any one of claims 1 to 7, characterized in that the solar cell efficiency is 17% or more. A solar cell comprising the solar cell substrate of claim 11 or 12, wherein the cell efficiency is 17% or more.

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